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Double Clutching - Put To Rest

Discussion in 'Racing and Driving Techniques' started by tdehnel, Feb 20, 2003.

  1. tdehnel

    tdehnel Senior Member

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    From reading some recent posts, it seems like there is some disagreement or ignorance as far as the exact and proper way to downshift using the double clutch method. I'll try to keep this simple as I describe a normal 4th to 3rd gear downshift:

    1. Driving along in 4th
    2. Depress clutch pedal
    3. Shift into 3rd
    4. Release clutch pedal

    Usually the engineers match the gear ratios well enough that this should all happen smoothly, but it can't be perfect all the time. The synchros do a lot of work in order to get the drive gear and 3rd gear spinning at the same time, and the wear on the synchros is what will cause that grinding sound over time. Now, if you want to preserve the life of your transmission, and look (and sound) cool doing it: follow these simple double clutch instructions. Remember, it's called double clutching because you use the clutch twice.

    1. Driving along in 4th
    2. Depress clutch pedal
    3. Shift into neutral
    4. Release clutch pedal
    5. Blip throttle
    6. Depress clutch pedal
    7. Shift into 3rd
    8. Release clutch pedal

    If you did it right, the shifter will slide effortlessly into place with no clicking or grinding sounds. If you followed the directions, but still met some resistance getting into 3rd gear, then you are blipping the throttle too much or too little.

    When you blip the throttle with the car in neutral it causes the engine and transmission to move at the same speed. If you blipped it just enough, this speed will be the same as the axles, too, and everything will come together.

    An important thing to realize is that the car is not in neutral if the clutch is in. The shifter must be in the middle of the transmission, and the clutch must be released for the car to be in neutral.

    If someone has told you that double clutching is revving the engine while the clutch is in, they are wrong. That only does half of the work and does not get the transmission up to speed.

    Here's a "diagram":
    ENGINE-TRANSMISSION-AXLES/WHEELS
    The transmission is right between the engine and the axles/wheels, so if you don't get the transmission moving, too, you're not double clutching.
     
  2. asmallsol

    asmallsol Super Moderator

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    What you said is basicly this
    2x clutching is pretty much only used when either your tranny is screw up (syncoros are going, going, gone) or your driving a really old car (ie 60's and stuff like that)
     
  3. tdehnel

    tdehnel Senior Member

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    lol I didn't know that existed, but I'm glad that confirms what I said.

    You're right, double clutching NEEDS to be used in those situations, but if you want a sustantially longer lasting transmission, use it in all driving situations. Those synchros do a great job, but they'll last a lot longer if you don't rely on them.
     
  4. asmallsol

    asmallsol Super Moderator

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    I try to use here and there but most of the time in normal traffic, it is hard to keep up just from a stop light because i am not sure how long you have to keep it in nuetral. About how long should it take.
     
  5. RFHOMI2U

    RFHOMI2U Senior Member

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    what about double-clutching during up-shifting? same way?
     
  6. tdehnel

    tdehnel Senior Member

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    asmallsol - You're right about those cars from the 60s. They don't have synchros and therefore a double clutch is absolutely neccessary to downshift. But your question confused me; are you trying to double clutch when you're accelerating?

    To address that and RFHOMI2U's question, do not use this while you are accelerating, there is no point because when you upshift, your engine speed decreases, and there's no need to speed up the engine with a throttle blip.

    Double clutching is used only for downshifting. I find it to be most useful in parking lots and pulling into driveways. Mostly at slow speeds. This technique makes it easy to downshift from second into first gear when you need to (to pull into a parking lot or parking space etc).

    Double clutching is not really a racing technique, and is definitely not a drag racing technique. It is just used for a smoother downshift, and to extend the life if your transmission.

    Most racers don't care about their synchros getting worn because after the race, the transmission gets rebuilt anyway, so there's no need to worry about taking care of the trans for one race. Smooth=fast in racing, but they use a technique that is not really double clutching at all, they simply blip the throttle when downshifting, but don't take their foot off the clutch. A lot of people do that while driving and think they are double clutching. My question is, how are you double clutching if you're only using the clutch once? To get back to those racers, when you're racing, you're just jamming the shifter into gear, with no worry about the synchros.

    When double clutching, a quick blip on the throttle is usually all that's needed. Just depress the gas pedal all the way down for a fraction of a second, a simple on/off motion.
     
  7. asmallsol

    asmallsol Super Moderator

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    Yes i know that It is really not a drag technique but in road racing, it makes for a smoother transitions going into turns. Once your coming through the turns this is when you use heel and toe. The major reason why heel and toe is diffrent from 2x clutching is because heel and toe you never really leave that gear, you just keep the shifter in the 2nd slot and just coast through the trun with the revs up and brakes coming into the turn.

    Basicly 2x clutching IS a racing technique because it make you use Engine braking instead of normal brakes.
     
  8. SixtySecondAssassin

    SixtySecondAssassin Senior Member

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    with heel toe the clutch is usually in. if not you could just use you left foot to brake.
     
  9. asmallsol

    asmallsol Super Moderator

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    That is what i ment by coast, and the shifter not leaving the second gear slot because if your syncros are shot like mine, sometimes they dont want to go back in if you talk the shifter out of slot during hard driving but your still free wheeling it because the clutch is in.
     
  10. tdehnel

    tdehnel Senior Member

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    Double clutching does not make you use engine braking. In actuality, you use engine braking more with regular shifting because the revs are not matched and if they are too low, the car will lurch as you take your foot off the clutch.

    Double clutching makes 2 things smoother:

    First, the actual motion of moving the shifter into gear is easier. This is the whole reason that double clutching was first used.

    Second, it makes for a smoother transition as you take your foot off the clutch, because everything is spinning at the same relative speeds.

    My whole point with saying that it's not a racing technique is that double clutching was first invented out of neccessity. The first cars had no synchros, which made downshifting almost impossible unless you used the double clutch technique. I agree that you can use it in racing, but it's slower than the fake double clutch because you don't just jam it into gear.

    What I was saying before is that for the effect you want "smoother transitions", there is a technique that is just like a normal downshift, but with one extra step:

    1. Driving along in 3rd
    2. Depress clutch pedal
    3. Shift into 2nd
    4. Blip throttle
    5. Release clutch pedal

    This technique which I call the "fake double clutch" makes the downshift smooth, but does not save wear on the synchros like real double clutching does.

    Go out and try all 3 shifts a few times, the regular downshift, the fake double clutch, and the real double clutch. You should have the following results. Pay attention to the feel of the shifter, notice how it is easier to put in gear with the real double clutch.

    Regular shift: uses synchros to get gear speeds equal (wear on synchros and non-smooth downshift)
    Fake Double Clutch: still uses synchros to mate gears, but smooth downshift (wear on synchros)
    Double Clutch: similar gear speeds don't rely on synchros to mate gears, downshift is smooth.

    Remember, although there's a lot of pedal work, the unique results of double clutching are felt when you move the actual shifter into a lower gear. It should slide right in.

    asmallsol - since your synchros are shot, you should be able to use double clutching to get yourself back in gear, unless you are doing it wrong.
     
  11. asmallsol

    asmallsol Super Moderator

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    Just sometimes my syncros are stubbron and just wont let me shift untill my speeds (expically engine speed) drop down, which is never good in autoX. I will actually go out for a little drive today and test it but like when i am coming up to a yeild sign (roll through at like 5-10mph) and if i want to put it in first, it basicly wont go in untill i am practicly stopped. If i leave it in second, i bog for a little bit (tad to slow for that gear) and what really sucks is in autoX, going through some of the really tight turns where you exit at about 10-18 mph, i have to be in second gear (dont even try to put in first, i know it wont go in) so i have to exit the turn will rpms around 2k, with a d16z6 (and most vtec engines, dohc or sohc) there is no trq there so for about a second there, you waiting for the high revs to return.
     
  12. tdehnel

    tdehnel Senior Member

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    Yeah, you could get it in first gear at those speeds, you just have to blip the throttle for longer to get the engine and transmission up to the relative speed of the wheels.
     
  13. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Thanks for the extra work... but yeah, I did write that article for a reason. More support from our members always helps though! :)
     
  14. pills_PMD

    pills_PMD Super Moderator

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    WHO THE FUCK CARES??? honestly.
     
  15. BigJ

    BigJ I'm just about that action Boss. VIP

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    Yeah I care man. I mean I am still learning good technique and stuff and down shifting is a have to and this helps a lot. I mean for a car that constantly comes out of second when you let off gas this is useful stuff to save the life of the synchros. Thanks guys for going so into depth on this stuff.
     
  16. tdehnel

    tdehnel Senior Member

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  17. EKDRIFTER

    EKDRIFTER Junior Member

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    hey guys...

    you guys said that DOUBLE CLUTCHING IS FOR DOWNSHIFTING...

    but why and i quote VIN DIESEL in the RICE AND THE FURIOUS after the BIG RACE of the 4 cars does he tell Brian this: "GRANNY SHIFTING, NOT DOUBLE CLUTCHING LIKE YOU SHOULD"... anyone remember right after they were checking out the BUSTED ECLIPSE ENGINE..

    dont know why he said that? supposedly they were RACING (UPSHIFTING)...

    anyone can explain? or should i go to www.movie-mistakes.com and put ANOTHER MISTAKE on that MOVIE...hehe
     
  18. asmallsol

    asmallsol Super Moderator

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    Oh well because Fast N Ferious said it, It must be true. Because i have seen so many rwd cars do burn outs and wheeiles at the same time. Just like Nawwss will make run .000002 second quarters on a stock D series engine or 17's or 18's will make you go faster.

    LEARN FROM FAST N FERIOUS BY NOT DOING WHAT THEY DO
     
  19. BigJ

    BigJ I'm just about that action Boss. VIP

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    meh and my buddy watch that movie once a week and point out probably in every scene what was wrong withit and all this stuff. I mean I love the car scenes just because they are cars but really its all bs stuff. The supra would have ripped the fricking maranello up all day but it seemed like he barely beat it and all this other stuff. PURE BS Oh yeah I am making a "remake" using my lawn mower that actually wheelies and spins em going into 3rd and 4th gear, we are using duct tape racing stripes and stuff for it, and using my buddies 83 camaro with t top to do the truck scene with the supra. I will maybe put on the computer when we make it this summer. It will be hella bad ass.
     
  20. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Sweet. I want to see that! :lol:
     
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